Joint compounds, activators and methods for setting a joint compound and preventing seed setting

Abstract

A ready-mixed setting type joint compound in which formation of gypsum seeds has been inhibited. A method for controlling a setting reaction by mixing a ready-mixed setting type joint compound with one or more metal ion control agents comprising aminopolycarboxylic acid and/or a salt thereof, and further mixing the setting type joint compound with one or more non-calcium phosphate compounds. The method may further comprise mixing the setting type joint compound with a set activator obtained by blending together a first set activator including a cadmium compound, lead compound and/or zinc compound and a second set activator including a ferrous compound, aluminum compound and/or manganese compound.

What is claimed is: 
     
       1. A method for inhibiting formation of gypsum seeds in a ready-mixed setting type joint compound, the method comprising:
 mixing at least calcined gypsum, water, at least one non-calcium phosphate compound and at least one metal ion control agent comprising an aminopolycarboxylic acid and/or a salt thereof, and thereby obtaining a ready-mixed setting joint compound, 
 wherein the metal ion control agent is used in an amount from about 0.01% to about 10% by weight of calcined gypsum; and 
 wherein the metal ion control agent inhibits formation of gypsum seeds in the ready-mixed setting type joint compound during storage; and 
 wherein the method further comprises blending together a first activator and a second activator, and thereby obtaining a set activator blend; and 
 mixing the set activator blend with the ready-mixed setting type joint compound; and 
 wherein the first set activator is zinc oxide, zinc hydroxide and/or zinc salt and wherein the second set activator is aluminum oxide, aluminum hydroxide and/or aluminum salt; 
 wherein the ratio of the first set activator to the second set activator in the set activator blend is in the range from 3:1 to 1:1 by dry weight of the first set activator to the second set activator, and the mixing of the set activator blend with the ready-mixed setting type joint compound is performed at a temperature in the range from 40° F. to 65° F., and wherein the set activator blend is added in an amount from 0.5% to 5% by weight to the setting joint compound, excluding water. 
 
     
     
       2. The method of  claim 1 , wherein the first set activator is zinc sulfate and wherein the second set activator is alum. 
     
     
       3. The method of  claim 1 , wherein the non-calcium phosphate compound comprises zinc hexametaphosphate, potassium tripolyphosphate, tetra sodium pyrophosphate, tetra potassium pyrophosphate, sodium tripolyphosphate, mono-ammonium phosphate, monobasic potassium phosphate, or any combination thereof. 
     
     
       4. The method of  claim 1 , wherein the metal ion control agent comprises diethylenetriamine pentaacetic acid (DTPA), pentasodium diethylenetriamine pentaacetate, calcium trisodium diethylenetriamine pentaacetate, ethylenediamine tetraacetic acid (EDTA), sodium calcium edetate, hydroxy-ethyl-ethylene-diaminetriacetic acid (HEDTA), trisodium N-(hydroxyethyl)-ethylenediaminetriacetate, or any combination thereof. 
     
     
       5. The method of  claim 1 , wherein from about 0.01% to about 10% by weight of the non-calcium phosphate compound is used, calculated as a percentage of the weight of dry calcined gypsum. 
     
     
       6. The method of  claim 1 , wherein the metal ion control agent comprises pentasodium diethylenetriamine pentaacetate in an amount from about 0.01% to about 10% by weight, based on the weight of dry calcined gypsum and wherein the non-calcium phosphate compound comprises tetra-potassium pyrophosphate (TKPP) in an amount from about 0.01% to about 10% by weight and/or tetra-sodium pyrophosphate (TKPP) in an amount from about 0.01% to about 10% by weight, all calculations based on the weight of dry calcined gypsum. 
     
     
       7. The method of  claim 1 , wherein at least one of the following is further mixed with the setting type joint compound: a binder, calcium carbonate, mica, talc, clay, a low molecular weight polymer, or any combination thereof.